Лучше уточнить этот момент на сайте Испании или Ирландии я думаю.
Про апостиль и нет ничего, но требуют, собаки. Французы особенно.
Вот французы:
Civil marriage certificate, original
•If your Marriage Certificate has been issued outside the European Union, it must be stamped by the Foreign Office of the issuing country, or its Embassy in the UK.
•If the marriage was celebrated in the UK by a religious authority, the marriage certificate must be paired with an official registration at the General Register Office.
Civil marriage certificate, copy
Civil marriage certificate, official translation
in French or English, this official translation must be certified as a true copy by the Embassy/ Consulate of the country where your marriage was celebrated or by the legalisation bureau of the Foreign Office in GB